[1] He was born on 4 May 1786 as the only son of William Fitzwilliam, 4th Earl Fitzwilliam, who served as Lord President of the Council and Lord Lieutenant of Ireland, and his first wife, Lady Charlotte Ponsonby (daughter of William Ponsonby, 2nd Earl of Bessborough).

[2] Before inheriting the Earldom on 8 February 1833 on the death of his father, he was known by the courtesy title of Viscount Milton.

Fitzwilliam became a strong supporter of Parliamentary Reform and one of the principal advocates of repeal of the Corn Laws.

[3][4][5] The family seat was Wentworth Woodhouse, reputedly the largest private house in England.

[7] They had thirteen children:[8] Lord Fitzwilliam died on 4 October 1857.